Work clamping means for machine tools



Dec. 12, 1944. w. H. WEIMER 7 WORK CLAMPING MEANS FOR MACHINE TOOLS Filed May 28, 1942 R EMW MW m AR M m v WT WM A m L H 1 1 a Patented Dec. 12,1944

- WORK CLAIWPINGMEAN S FOR MACHINE I .TOOLS William HQWeimer, North Prairie, Wis., assignor to Davis & Thompson Company, West Wis., a corporation of Delaware Allis,

- Application May 28, 1942, Serial No. 444,871 v 8 Claims. (CL 29-26) The presentinvention relates to machine tools, and more particularly to means for feeding and clamping the work.

A type of work clamping means for metal vide an improved work clamping means of the tensioned band type which is so constructed as to have a wide range of clamping action and to minimize variations in clamping pressure during the movement of theuwork carrier.

Another object is to provide simple but effective means for locally releasing the tensioned clamping band from clamping engagement, so as to facilitate tool changes or adjustments.

Still another object is to support the work clamping portion of the band in such manner as to facilitate the feeding and clamping of work pieces of different size.

A further object is to provide supporting means for the work-clamping portion of the band including a shiftable part which-is yield able toward and awayfrom the'band 'during the movement of the carrier, so as toaccommodatethe changing position of the work and to retain the work firmly on the carrier. A still further object is to perfect details of construction generally. a

i The invention further-consists in the several features hereinafter described and claimed.

In the accompanying drawing,

Fig. 1 is a transverse sectional elevation of a milling and drilling machine equipped with work clamping mechanism embodying the invention, parts being broken away'and parts being sh'ownin section;

h Fig. 2 is a front-elevation, parts of the work clamping mechanism being broken away and 1 In the drawing, the work clamping media-- nism ofthe invention is shownto be applied to a combined milling and drilling. machine, although the mechanism may be used on varioustypes of machine tools. 1 The machinedllustrated includes a frame l0 havinghorizontal ways It and further includes a rotatable work carrier which comprises a mandrel or arbor l2 extending parallel to the ways and provided with a work holding fixture [3. At its periphery thefixture has a, series of work-receiving. jaws l4 formed by hardened renewable V blocks and adapted to position work pieces or blanks W. For. long work pieces, such as shafts or gun barrel forgings, the fixture maybe formed of two or more parts axially spaced on the mandrel, asis well understood in this art. The work carrier may be modified in various ways to suit. the ,work at hand.

The machine is provided with roughing ,and finishing milling cutters l5 and 16,-respectively; for facing the ends of the work pieces, and is. further provided with centering drills H for forming center holes in the faced ends of the work pieces. Each drill is detachably carried in a rotatable chuck l8, Fig-'2, which is suitably mounted for reciprocation in a housing l9. 7

By way of example, the. three successive operations, rough facing-finish facing, and drillingare effected at stations spaced 45 apart, the drilling station being at the top of the carrier; The work carrier rotates intermittently, being indexed to its successive positions in any well known manner. However, it is also possible to provide for continuous rotation of the work carrier, as is well understood in this art.

A tensioned work clamping band 20, such .as a block chain, is mounted on grooved guide pulleys or sheaves 2|, 22, 23, 24 and 25 having v parallel axes, the band lying in a plane normal to the axis of the workrcarrier and the pulleys being distributed about the carrier. The pulleys are so related to eachother as to permit a reentrant open loop or bend 26 being "formed in the chain to pass about the work carrier and to hold the work piecesin the carrier jaws I4. The work clamping portion of the loop ishere shown to extend over about four-fifths of: the- The frame 21 further includes a housing 29 which is secured to the rear portion of the base on the shaft 32 and is disposed between the ears. A swingable hollow housing or arm 33 of-. U-shaped cross section is pivotally carried at its lower,

in the side walls of the housing, these slots extending upwardly and rearwardly. A rod 59 extending parallel to the slots 58 is screw-threaded in the top portion of the housing and has a swivel The pulley Z2 is. mounted-1' connection 60 with the yoke, so as to permit raising and lowering of the yoke by rotating the screw. By raising the pulley a sufficient distance the chasm-2B WillE'bB released from clamping engagement with the topmost work piece, as seen in Fig. 3, so as to facilitate the replacement of broken drills or other manipulation of the drill- :fingmeans; However, the work pieces at both umilling stations will remain in clamped position,

' to. workpieces ct different diameter it is someportion on the shaft 32 and projects upwardly in.

front of the work carrier, the open rear portion of the arm facing the work carrier. The pulley 2| is housed within the upper portion. of they swingable arm 33 and is mounted on a shaft 34 carried'by the-arm ata point somewhat higher l than the axi's of the workcarrier'. From thefront; portion of the clampin -loop2$ the chain passes over the pulley 2|, thence downwardly withinthe'a-rm 33 to the pulley 22; and th'ence along the base member Z B -to the rear ofi the machine.

The arm- 33 is swingabl'e forwardly and; rearward-1y, and its rearward movement toward the carrier is adjustabl y limited by astud 35 'carried by the base member" andg' extendin'g'through a slot a lug 3-! formed on the l'owerportion of the arm, the stud carrying thereon an adjustable nut' 38. The swinging arm 33 serves to keep the a chain in contact: with the workpieces, so:- as to retain them in the jaws M at the descendingpart'of th'e rotatable work carrier, and is yieldable outwardly to acconunodate the changing position of the work pieces during rotation of the-carrier, and: also to accommodate changes in the'diameter of the work; The hollowiarnr 33 also forms: a guard or enclosurefor the pulleys 25b and 22 and: fertile: adjacent portion the chain'261 The pulley 2391s located at thelowerportiorr of;

the housing 29 and to the rear. ofthe carrier; and is carried on a shaft 39': mounted in atyoke M): slidably fitting between the spaced-Q pressed coil spring 44" surrounding the: rod; the

spring being confinedfbetweem washers: 45 and 4E andibeingretainedi by." a nut ti whiclrlis adjustable: tcrvary the spring pressure The puli'ey 24b is: located. at: the. upper." rear poz-- tion ofi the housing 2.9 and; is arranged:v the puHey 23, being carriedz'by a shaft dit'mountedi ina' yoke the ends of the: shah:

guided in: horizontal slots 53? in the hdusingisid wall.

beingadj-ustableby a nutifi on the rod,

Thepulley- 25 is, located: at the front portion ofthe. housing. 29 above the work carrier and;

forwardly of the vertical plane'of the carrier: axis:

and is carried. on a shafit-EG: whichismount edx in a yoke- 51,. the pulley being {disposed between I the legs of the: yoke; The ends of; the shaftfisitare Slidablvguieled in inclined slots 58' formed.

The yoke carries-a rods 52!: projecting manwardly through: the housing and: is urged rearrwardlyyby a compressecfi coiled: spring. 522-d-iSpOSEdf between washers. 53: am 54;.the pressure and th raising ofthe pulley 25 will not materiallychange the chain tension. When changing times desirable to slightly change the elevation of the pulley25 and also the compression of the springs. and 52, the use of two springs permitting a wide range of adjustment and also distributmg the. displacement of: these: springs and the; pulleys. 231 and. 24.. The elevation. of the drill is adjusted in any suitable manner in. ac.- cordance with the diameter: of work.

- operation, the. work: carrier I2; [-3 rotates intermittently.- I in; the direction: indicated: by the arrovm; being indexed to. the: stationary position showninliig. 1;. The. work-pieces are; loaded onto thezcarri'er at the-station marked; Loadfiand. the finished. work pieces. are unloaded-1 at. the same statmn. The; newly introduced: work: pieces: first move; downwardlyawith the rotating carrier, :being retaineciimthe carrierjaws 'by the fiont' portionof the chain loop 26. During indexing of thecarrich-through: successive 45 intervals: the. swingabl'e arm 33 will. yield rearward-1y and forwardly,

so as to: follow the work. pieces and retainthem inthe-jiawsb The work-pieces on the rotatable carrier successively reach the stations. marked;

Rough out, Finish. cut and Drillecenterfi At are automatically: clamped on the; movable can rier and areautomaticaflly released afterthe final tool operation-. Howeventhgwork piece-in the final. tooling. position. can. be manually released; as above described, without affecting the clamped: condition of the succeeding work. pieces, and. if necessary the released work piecelcan be removed from the. machine, as for. the purpose of. extracting a; broken drill enel;.. The, inward and. out,-

ward displacement of the-sW-ingablearm 33 does not materially affect the chain tension, and this tension remains approximately uniform during carrier the milling cutters arepreferalcrly'moveciiin; a transverse, directionzto" and: away from. the

work while the: carrier is stationary, whereas v the case of a continuously rotatablexwork'car rier the cutter-axes are. preferably fixed; I

When settingupitheimachine to operate on work pieces of diflerent dia'metenit isisometime's: desirable to substitute-jawblocks Hit of difierenti thickness, so as to avoid-any appreciablechange m the distance from: the. carrier axisto the den adapted to travel with the carrier for clamping the work on the carrier, means for supporting the band including a pulley adjacent to said carrier and adapted to receive the hand thereon, and means for shifting said pulley away from said carrier to release locally a portion of said tensioned band from clamping position while maintaining the tension on said band.

3. In a machine tool, the combination, with 'a rotatable work carrier, of a tensioned clamping band having a reentrant loop extending partially about said carrier for clamping the work on the carrier, means for supporting said band including guide members adjacent to said carrier at the end \portions of said loop, there being a passage between said guide members for admission of workpieces to the carrier, and shiftable means for supporting said guide members to permit displacement of said guide members toward and away from said carrier while'maintaining the tension on said band.

4. In a machine tool, the combination, with a movable work carrier, of a tensioned band including a clamping portion for holding the work on the carrier, and means for supporting said balnd including a shiftable ,member normally urged towardsaid carrier and yieldable away from said carrier during the travel of the work while maintaining the tension on said band.

5. In a machine tool, the combination, with a movable work carrier, of a tensioned band including a*clamping portion for holding the work on the carrier, means for supporting said band including a pulley adjacent to the carrier and over which pulley the band reversely passes, and a swingably mounted arm for supporting said pulley for movement toward and away from the carrier and approximately at, right angles to the portions of saidband extending from said pulley so as to permit the swinging movement of said pulley-supporting arm while maintaining the tension of said band.

6. In a machine tool, the combination, with a movable work carrier, of a tensioned band including a clamping portion for holding the work on the carrier, means for supporting said band including a pulley adjacent to the carrier and over which p ulley the band passes, and a swingably mounted arm for supporting said pulley for movement toward and away from the carrier, said band supporting means including a second pulley approximately coaxial with the pivotal axis of said arm.

'7. In a machine tool, the combination, with a movable work carrier, of a tensioned band including a clamping portion for holding the work on the carrier, means for supporting said band including a pulley adjacent to the carrier and over which pulley the band passes, a swingably mounted arm for supporting said pulley adjacent to the work-loading region of said carrier for work-confining movement toward and away i drilling position, of a tensioned band for clamp- 0; ing the work pieces on, the carrier, and shiftable means for locally releasing a portion of said tensioned band from clamping condition with respect to a work piece in its drilling position while maintaining the tension on said band. I 

